My"e*lin (?), n. [Gr. marrow.]
(Physiol. Chem.) (a) A soft white
substance constituting the medullary sheaths of nerve fibers, and
composed mainly of cholesterin, lecithin, cerebrin, albumin, and some
fat. (b) One of a group of phosphorized
principles occurring in nerve tissue, both in the brain and nerve
fibers.